Better way to retrieve the values of all public state variables of a Solidity contract

Question

My solidity "0.7.0" contract

pragma solidity ^0.7.0;

contract DoubleEscrowTrade {
    uint256 private locked = 2; //2: unlocked, 1: locked. uint256 is gas efficient than bool
    uint256 public value=0;  //poster value
    uint256 public bidItemValue=0;  //bidder item value
    bool public openForBid = false;  //allow items with any value to bid.
    string public posterItemName;
    string public whoInitDispute;
    uint256 public posterItemID;
    string public bidderItemName; //no string array supported
    uint256 public bidderItemID;
    mapping (address=>address) public bidItemAddress; // bidder address and bidder item deploy address
    mapping (address=>uint256) public bidItemID;
    mapping (address=>uint256) public bidValue;
    mapping (address=>string) public bidItemName;
    uint256 public howManyBidItem=0;
    address payable public poster;
    address payable public bidder;
    bool public delisted = false;
    bool public posterDispute = false;
    bool public bidderDispute = false;
    bool public posterShipped = false;
    bool public bidderShipped = false;
    uint256 public posterReceiveProdTime = 0;
    uint256 public bidderReceiveProdTime = 0;
    uint256 public posterReceiveReturnTime = 0;
    uint256 public bidderReceiveReturnTime = 0;
    uint256 public posterAcceptBidTime = 0;
    uint256 public posterEscrowBalance = 0;
    uint256 public posterEscrowRefund = 0;
    uint256 public bidderEscrowBalance = 0;
    uint256 public bidderEscrowRefund = 0;
    uint256 public bidderShipProdTime = 0;
    uint256 public posterShipProdTime = 0;
    uint256 public posterDepositTime = 0;
    uint256 public bidderDepositTime = 0;
    uint256 public posterDisputeTime = 0;
    uint256 public bidderDisputeTime = 0;
    uint256 public posterDelistTime = 0;
    uint256 private graceDay = 14;
    uint256 private dayInSecond = 24*3600;
    enum State { ForTrade, PosterAcceptBid, PosterEscrowDeposited, BidderEscrowDeposited, PosterDelisted, BidderCancelled, BidderShipped, PosterShipped, 
    InDispute, Complete, PosterReceiveProduct, PosterReceiveReturn, BidderReceiveProduct, BidderReceiveReturn }
    State public state;

The public variables include address, mapping, uint256, string and bool. The app can get value for a public variable myVar with myContract.myVar(). However there will be excessive number of requests with so many variables and it is tedious as well. Based on my reading, I probably can get all uint256 variables with return (var1, var2, ... varN) in an array. But I am not sure if mapping, bool, string and address can be all returned within one return in solidity 0.7.0. Or there is a even better way to handle this.

Answer 1

By return(<...>) you can return not so many values. These values will be returned in a stack and compiler doesn't let you make the stack too deep. It is independent of variables type. There are many variables in the contract code and I am almost sure that you can't return all them by just one return(<...>).

By observing the number limit in the returned values in return(<...>), You can return public bool, string, address, and mapping by it.

Answer 2

I had a similar issue, and there are a few approaches to this.

1.You can -as you had noted- return it all one by one.

2.You can try to pack it all into a single huge array.

3.You could return multiple arrays. One containing addresses, the other one containing uint256 variables etc.

In your case (If you don't need an entire map, but just a single value mapped here). I would advise using an array of strings that returns all the values as such. In that way, all the data will be preserved in a nice readable format.

However, to return an array of strings you need to add [pragma experimental ABIEncoderV2; ] to your code.

Like this:

pragma solidity ^0.7.0;
pragma experimental ABIEncoderV2; // Added experimental encoder

contract DoubleEscrowTrade {
    uint256 private locked = 2; //2: unlocked, 1: locked. uint256 is gas efficient than bool
    uint256 public value=0;  //poster value
    uint256 public bidItemValue=0;  //bidder item value
    bool public openForBid = false;  //allow items with any value to bid.
    string public posterItemName;
    string public whoInitDispute;
    uint256 public posterItemID;
    string public bidderItemName; //no string array supported
    uint256 public bidderItemID;
    mapping (address=>address) public bidItemAddress; // bidder address and bidder item deploy address
    mapping (address=>uint256) public bidItemID;
    mapping (address=>uint256) public bidValue;
    mapping (address=>string) public bidItemName;
    uint256 public howManyBidItem=0;
    address payable public poster;
    address payable public bidder;
    bool public delisted = false;
    bool public posterDispute = false;
    bool public bidderDispute = false;
    bool public posterShipped = false;
    bool public bidderShipped = false;
    uint256 public posterReceiveProdTime = 0;
    uint256 public bidderReceiveProdTime = 0;
    uint256 public posterReceiveReturnTime = 0;
    uint256 public bidderReceiveReturnTime = 0;
    uint256 public posterAcceptBidTime = 0;
    uint256 public posterEscrowBalance = 0;
    uint256 public posterEscrowRefund = 0;
    uint256 public bidderEscrowBalance = 0;
    uint256 public bidderEscrowRefund = 0;
    uint256 public bidderShipProdTime = 0;
    uint256 public posterShipProdTime = 0;
    uint256 public posterDepositTime = 0;
    uint256 public bidderDepositTime = 0;
    uint256 public posterDisputeTime = 0;
    uint256 public bidderDisputeTime = 0;
    uint256 public posterDelistTime = 0;
    uint256 private graceDay = 14;
    uint256 private dayInSecond = 24*3600;
    enum State { ForTrade, PosterAcceptBid, PosterEscrowDeposited, BidderEscrowDeposited, PosterDelisted, BidderCancelled, BidderShipped, PosterShipped, 
    InDispute, Complete, PosterReceiveProduct, PosterReceiveReturn, BidderReceiveProduct, BidderReceiveReturn }
    State public state;